Wireless base station and a wireless phone

ABSTRACT

On receiving a link channel assignment request or a link channel reassignment request from a mobile station, a wireless base station specifies a unique word (UW) that is not assigned to any other mobile stations, and sends a channel assignment notification containing the specified UW to the requesting mobile station. The base station also sends the specified UW to its user processing unit, which extracts a signal sent from the requesting mobile station and generates a signal to be sent to this mobile station. The base station then defines a reference signal based on the sent UW, and adjusts each weight vector by using the defined reference signal and a signal estimated to have been sent from the requesting mobile station, thereby directing the directivity pattern to the requesting mobile station.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a wireless base station that wirelesslycommunicates with a plurality of mobile stations, such as PHS (PersonalHandyphone System) mobile phones and cellular phones, by using SDM(space division multiplexing), and to a communication technique thereof.

(2) Description of the Prior Art

As the increasing number of mobile stations, such as a PHS mobile phoneand a cellular phone, are in widespread use, the need for effective useof a limited number of transmission frequencies arises high. The SDM(Space Division Multiplexing) is one method responding to such need.

With the SDM, a wireless base station simultaneously communicates with aplurality of mobile stations located in various directions via the samefrequency, using directional antennas.

An adaptive array antenna device is one form of such directional antennaused in the SDM communication. The adaptive array antenna devicecomprises a plurality of antenna elements that are fixed, and shapes adirectivity pattern (which is also called an array antenna pattern) usedfor signal transmission and reception by dynamically changing anamplitude and a phase of a signal received/sent via each antennaelement.

When producing a directivity pattern, the adaptive array antenna devicenot only raises sending strength and receiving sensitivity in adirection in which a desired. mobile station exists, but also lowerssending strength and receiving sensitivity in a direction of othermobile stations with which he base station communicates using the SDM.The detailed explanation of an adaptive array antenna device is given by“Special Papers on Signal Processing in a Space Domain and Technologythereof” in The Institute of Electronics, Information, and CommunicationEngineers Transaction VOL. J75-B-2 No. 11.

In a wireless base station that uses an adaptive array antenna device assending/receiving antennas, the directivity pattern is changed inaccordance with a movement of each mobile station so as to minimizeinterference caused by other connections and maintain good transmissionquality. The following describes operations to control directivitypattern shaping according to a minimum mean squared error (MMSE) methodwhen a signal is received or sent with an assumption that the totalnumber of antenna elements included in the adaptive array antenna deviceis “N”.

For a signal reception, the directivity pattern is controlled so as toseparate a signal, which has been sent from a desired mobile mobilestation, from data into which a plurality of signals of other mobilestations are multiplexed.

FIG. 9 shows representation of the MMSE controlling operation onperformed when the adaptive array antenna device receives signals frommobile stations.

Expression 1y(t)=w(t−1)·x(t)=w ₁(t−1)·x ₁(t)+w ₂(t−1)·x ₂(t)+ . . . w _(N)(t−1)·x_(N)(t)

In Expression 1, “x₁(t)”, “x₂(t)” . . . “x_(N)(t)” each represent avector of a reception signal received via one of the antenna elements,and “w₁(t−1)”, “w₂(t−1)” . . . “w_(N)(t−1)” each represent a weightvector corresponding to each antenna element. As shown in the figure andExpression 1, a sum of reception signal vectors multiplied by weightvectors corresponding to the plurality of antenna elements is regardedas a signal “y(t)” sent from a desired mobile station. A value of eachweight vector needs to be adjusted to correctly obtain the desiredsignal “y(t)”

In Expression 1, “t” represents a time at which a signal is received byeach antenna element. For instance, “t” may be a value showing anelapsed time represented in a unit of a time required to receive onesymbol within a time slot in a standard related to PHS system in Japan.Hereafter, this standard is called a “PHS standard”. Accordingly, avalue of “t” in each of the above reception signal vectors “x” andweight vectors “w” changes from “1” to “2” . . . , and so each of thereception signal vectors and weight vectors is a signal sequence. Eachweight vector is a parameter used for shaping the directivity pattern.Each weight vector and each reception signal vector is a signal, whichis shown as a complex vector and has an amplitude and a phase.

Each weight vector has a predetermined value as its initial value. Thisinitial value is updated within a predetermined range at predeterminedtimes in a manner that minimizes an error between the desired signal“y(t)” and a reference signal “d(t)”. The reference signal “d(t)”contains a part, such as a preamble (PR) and a unique word (UW) forsynchronization defined in the PHS standard, of a signal sent from amobile station, and has a predetermined fixed value.

Expression 2e(t)=d(t)−y(t)=d(t)−w(t−1)·x(t)

This is to say, a weight vector “w(t−1)” is adjusted to “w(t)” so as tominimize the error “e(t)” between the reference signal “d(t)” and thedesired signal “y(t)”, i.e., the separation result. In theory, a wightvector converges to a certain value over time so that quality of thedesired signal “y(t)” gradually raises. Since a mobile station firstsends a PR and a UW making up the reference signal, and then sends bodydata (the content of the communication), quality of the desired signal“y(t)” somewhat improves by the time the body data is received. After aphone conversation starts, a value of the weight vector obtained in theimmediately preceding time slot is used as the initial value of thecurrent wight vector.

When interference between different connections of a plurality of mobilestations is not likely to occur due to locations of the mobile stationsor for other reasons, the wireless base station not only uses the SDM,but also shapes the directivity pattern in accordance with directions ofthese mobile stations, or staggers receiving/sending times for theplurality of mobile stations by a duration taken by, for instance, atransmission of one symbol in each time slot so as to minimizeinterface.

For a transmission to each mobile station, the directivity pattern iscontrolled as follows. A signal to be sent to a desired mobile stationis distributed to each antenna element. After this, another signal isgenerated by multiplying, for each antenna element, the distributedsignal by a weight vector that was lastly obtained corresponding to eachantenna element during reception. After this, all the plurality ofantenna elements simultaneously transmit generated signals. As a result,the directivity is pointed to the desired mobile station, so thattransmit gain control is achieved, and an unnecessary signal is nottransmitted to other interfering users.

In this way, during a reception of a signal, the wireless base stationadjusts wight vectors based on: (a) signals received via a plurality ofantenna elements; and (b) information, such as a PR and an UW, which haspredetermined content. By doing so, the wireless base station canextract a desired signal from other signals. During a transmission to amobile station, the wireless base station points the directivity to themobile station using the above weight vectors used during the reception.In this way, the wireless base station communicates with differentmobile stations using the SDM while minimizing interference to maintainrelatively good communication quality.

SUMMARY OF THE INVENTION

Under the control of the above conventional wireless base station,interference with other connections are suppressed such as by preciselystaggering sending times of different mobile stations communicating withthe base station using the SDM. Without using such complexinterference-suppressing method, the present invention aims to provide awireless base station and a wireless phone (mobile station), with whichinterference can be suppressed to maintain good communication quality.

To achieve the above object, a wireless base station of the presentinvention wirelessly communicates with a plurality of mobile stations byusing space division multiplexing (SDM). Each mobile station sendscommunication data containing an identifier (ID) to the wireless basestation. The wireless base station includes: an association informationstoring unit for storing association information that associates each ofthe plurality of mobile stations with a different ID; a receiving unitfor receiving data into which communication data sent from the pluralityof mobile stations is space-division multiplexed; and an extracting unitfor (a) specifying an ID associated with each mobile station byreferring to the association information, and (b) extracting, from thereceived data, communication data sent from the mobile station by usingthe specified ID.

For this construction, the plurality of mobile stations each sendcommunication data containing a different UW to the mobile station. EachUW is used as a part of a reference signal, which is used to correctlyseparate and extract communication data, which has been sent from adesired mobile station and multiplexed into a received signal, accordingto the MMSE method or the like. In accordance with results of theextraction, the base station can suitably direct the directivity patternin a direction of each mobile station. Accordingly, the base station cancommunicate with each mobile station using the SDM while reducinginterference and maintaining good communication quality.

Here, the association information may include a plurality of IDs andstate information that shows the plurality of mobile stations as beingassociated with the plurality of IDs. The wireless base station mayfurther include: a request receiving unit for receiving a request forassignment of a channel from a mobile station out of the plurality ofmobile stations; and an assigning unit for (a) specifying an ID for therequesting mobile station when the request has been received, whereinthe specified ID differs from an ID associated with another mobilestation, with which the wireless base station currently communicatesusing the UWs, (b) updating the state information by associating thespecified ID with the requesting mobile station, and (c) sendinginformation to the requesting mobile station, wherein the sentinformation shows the specified ID and a channel assigned to the mobilestation.

The above wireless base station sends a UW to a requesting mobilestation when assigning a channel to the mobile station. This UW differsfrom UWs that have been sent to other mobile stations that communicatewith the base station using the SDM, and therefore the requesting mobilestation can send communication data containing this UW differing fromother UWs. This allows the base station to suitably separate and extractthe sent communication data.

Here, the wireless base station may further include an associationdeleting unit for deleting, when a communication with a mobile stationis completed, an association between the mobile station and anassociated ID from the association information.

After completing SDM communication with a mobile station, the abovewireless base station can assign a UW which was associated with thismobile station to another mobile station with which the base stationstarts communication.

Here, the wireless base station may further include: an ID receivingunit for receiving an ID from a mobile station out of the plurality ofmobile stations; and an updating unit for updating the associationinformation by associating the received ID with the mobile station thatsent the ID when the ID has been received.

For this construction, the wireless base station can use a UW sent froma mobile station as a part of a reference signal. By using thisreference signal, the wireless base station can correctly extractspace-division multiplexed communication data of the mobile station froma signal according to the MMSE method.

Here, the wireless base station may further include: an ID receivingunit for receiving an ID from a mobile station out of the plurality ofthe mobile stations; and a sending/updating unit for (a) referring tothe association information when the ID has been received, (b) notifyingthe mobile station that an ID differing from the received ID should besent if the association information associates the received ID withanother mobile station, and (c) updating the association information byassociating the received ID with the mobile station that sent the ID ifthe association information does not associate the received ID with anymobile station.

This construction prevents a mobile station from using the same UW asused by another mobile station communicating with the wireless basestation using the SDM.

Here, for the wireless base station, when the receiving unit hasreceived the data, the extracting unit may also (a) obtain a pluralityof first signals from the received data, (b) obtain a second signalestimated to have been sent from each of the plurality of mobilestations, using the plurality of obtained first signals and a pluralityof weight vectors that are vector factors, (c) specify an ID associatedwith each mobile station by referring to the association information,(d) define a reference signal containing the specified ID, (e) compare acomponent of the defined reference signal with a component of theobtained second signal to detect a difference between the twocomponents, each component corresponding to a same predetermined period,(f) adjust the second signal by adjusting each weight vector so as tominimize the difference, and (g) regard the adjusted second signal ascommunication data sent from the mobile station, thereby extracting thecommunication data.

For this construction, it is possible to use a UW as a reference signaland to adjust each weight vector using this reference signal accordingto the MMSE method. Therefore, the wireless base station can correctlyseparate and extract a signal sent from each mobile station, andsuitably direct the directivity pattern to each mobile station to send asignal.

The present invention also relates to a wireless phone, including: areceiving unit for receiving an identifier (ID) sent from a wirelessbase station; and a sending unit for sending communication datacontaining the received ID to the wireless base station.

With this construction, each mobile station sends communication datacontaining a UW which has been assigned by the wireless base station. Byhaving the wireless base station assign a different UW to each mobilestation with which the base station communicates using the SDM, itbecomes possible for the wireless base station to suitably separate andextract communication data of each mobile station.

BRIEF DESCRIPTION OF THE DRAWINGS

These and the other objects, advantages and features of the inventionwill become apparent from the following description thereof taken inconjunction with the accompanying drawings which illustrate a specificembodiment of the invention.

In the drawings:

FIG. 1 is a block diagram showing a construction of a wireless basestation 1000 of the first embodiment;

FIG. 2 is a block diagram showing a signal processing unit 50;

FIG. 3 is a block diagram showing a user processing unit 51 a;

FIG. 4 shows a data construction and example contents of unique word(UW) information;

FIG. 5 is a flowchart showing the processing of the wireless basestation 1000 when it receives a link channel assignment request from amobile station to start data transmission or telephone conversation withthe mobile station;

FIG. 6 shows the sequence of link channel assignment in outline betweena mobile station and the wireless base station 1000;

FIG. 7 is a flowchart showing the processing of a wireless base stationof the second embodiment when it receives a link channel assignmentrequest from a mobile station to start data transmission or telephoneconversation with the mobile station;

FIG. 8 shows the sequence of the link channel assignment in outlinebetween a mobile station and the above wireless base station; and

FIG. 9 shows representation of the MMSE controlling operation performedwhen an adaptive array antenna device receives signals from mobilestations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes a wireless base station and mobile stations ofthe present invention, using several embodiments.

FIRST EMBODIMENT

Construction

FIG. 1 is a block diagram showing a construction of the wireless basestation of the first embodiment.

The wireless base station 1000 uses the SDM method as well as a TDMA/TDD(Time Division Multiple Access/Time Division Duplex) method. Thewireless base station 1000 wirelessly communicates with mobile stationswhich are PHS mobile phones by multiplexing four signals at most in theSDM via the same frequency. Hereafter, when a signal is multiplexed inthe SDM and the TDM, the signal is said to be “SD-multiplexed” and“TD-multiplexed”, respectively. The wireless base station 1000 comprisesantennas 11˜14, radio units 21˜24, a signal processing unit 50, a modemunit 60, a baseband unit 70, a control unit 80, and a UW storing unit90.

The wireless base station 1000 has four channels in each TDMA/TDD framein accordance with the PHS standard, and processes, in parallel, foursignals for four telephone lines, which are SD-multiplexed into a singlechannel. Each TDMA/TDD frame corresponds to a duration of five msec andis divided into eight time slots composed of four sending time slots andfour receiving time slots. Each time slot corresponds to a TDM/TDDchannel.

The baseband unit 70 transfers a plurality of signals, such as abaseband signal for sound or data, between the signal processing unit 50and a telephone switching network connected to a plurality of telephonelines.

The modem unit 60 modulates and demodulates a digitized baseband signalaccording to π/4 Shift QPSK (Quadrature Phase Shift Keying). Thismodulation and demodulation are performed in parallel on four TDMA/TDDframes at most that are SD-multiplexed in each TDM/TDD channel.

The signal processing unit 50 controls shaping of a directivity patternunder the control of the control unit 80. In more detail, from each ofthe radio units 21˜24, the signal processing unit 50 receives a signaland separates, from the received signal, a signal which has been sent bya mobile station and SD-multiplexed into the received signal. The signalprocessing unit 50 then sends the separated signal to the modem unit 60.The signal processing unit 50 also receives signals from the modem unit60, generates a signal using the received signals to be SD-multiplexed,and sends the generated signal to a corresponding radio unit out of theradio units 21˜24 so as to allow each signal sent from the modem unit 60to be transmitted to a desired mobile station. The signal processingunit 50 can be achieved by a programable DSP (Digital Signal Processor).Using the aforementioned MMSE method, the signal processing unit 50shapes the directivity pattern for each time slot in four or lessTDMA/TDD frames, which are processed by the modem unit 60 in parallel.During a reception of a signal from a mobile station, the signalprocessing unit 50 shapes the directivity pattern by adjusting eachweight vector in such a way that minimizes an error between a referencesignal and a signal estimated to have been sent from a desired mobilestation. This estimated signal is a sum of weight vectors of the radiounits 21˜24 multiplied respectively by signals received by the radiounits 21˜24. During a signal transmission to a mobile station, thesignal processing unit 50 shapes the directivity pattern by distributingsignals to the radio units 21˜24 based on weight vectors that wereobtained during the most recent reception.

Note that the signal processing unit 50 shapes the directivity patternin accordance with the SDM to send and receive a signal only when thetransmission is performed via a traffic channel (hereafter, “Tchannel”). When a signal is transferred via other control channels, thewireless base station 1000 controls this transfer in a similar way to aconventional wireless base station without using the SDM. Also note thata different reference signal is used for each mobile station, and thiswill be described in detail later.

The radio units 21˜24 have the same construction. The radio unit 21, forinstance, includes a sending unit 111 and a receiving unit 112, whichrespectively contain a high-power amplifier and a low-noise amplifier.

The sending unit 111 receives a LF (low frequency) signal from thesignal processing unit 50, converts the received LF signal into an HF(high frequency) signal, and amplifies the HF signal to a sending poweroutput level. The sending unit 111 then outputs the amplified HF signalto the antenna 11. The sending unit 111 controls the sending poweroutput such as by controlling a gain of the high-power amplifier undercontrol of the control unit 80.

The receiving unit 112 receives an HF signal which has been received bythe antenna 11, and converts the received HF signal into a LF signal.The receiving unit 112 then amplifies the LF signal, and outputs theamplified LF signal to the signal processing unit 50.

The control unit 80 is achieved specifically by a CPU (centralprocessing unit), memory, and the like, and controls other units of thewireless base station 1000 by having the CPU execute a program stored inthe memory.

The UW storing unit 90 stores a plurality of UWs to be assigned to aplurality of mobile stations whose signals are SD-multiplexed together.The UW storing unit 90 also stores UW information, which associates eachUW with a different mobile station to which the UW has been assigned.This UW information will be described in detail later.

FIG. 2 is a block diagram showing a construction of the signalprocessing unit 50.

The signal processing unit 50 includes send/receive switches 561˜564,adders 551˜554, and user processing units 51 a˜51 d.

The user processing units 51 a˜51 d adjusts a weight vector in each timeslot of a TDMA/TDD frame so as to correctly transfer a signal to/fromeach mobile station. In more detail, the user processing units 51 a˜51 deach receive signals X1˜X4 which are respectively outputted from theradio units 21˜24. The user processing units 51 a˜51 d also outputssignals Sa˜Sd to the radio units 21˜24. This is to say, the userprocessing units 51 a˜51 d each extract a signal of a desired mobilestation, and generates a signal to be outputted to the radio units 21˜24from signals which are outputted by the modem unit 60 and which includea signal, to be sent to the mobile station.

The send/receive switches 561˜564 are switched under the control of thecontrol unit 80.

The adders 551˜554 each add signals adjusted by the user processingunits 51 a˜51 d together to generate a signal, and outputs the generatedsignal to one of the radio units 21˜24.

FIG. 3 is a block diagram showing a construction of the user processingunit 51 a.

The user processing unit 51 a includes multipliers 521˜524 and 581˜584,an adder 59, a send/receive switch 56, a reference signal generatingunit 55, a weight calculating unit 58, and a weight selecting unit 57.

The reference signal generating unit 55 generates a reference signalwhich is an ideal signal estimated to have been sent from a desiredmobile station, using a UW and information fixed in the PHS standard,other than the UW. This fixed information contains a start symbol (SS)and a PR. The UW used to generate a reference signal is outputted fromthe control unit 80 to the reference signal generating unit 55. Sincethe control unit 80 outputs a different UW to each user processing unit,reference signals generated by reference signal generating units in theuser processing units 51 a˜51 d differ from one another.

The weight calculating unit 58 adjusts a weight vector in the MMSE. Inmore detail, the weight calculating unit 58 multiplies signals X1˜X4outputted respectively from the radio units 21˜24 by weight vectorscorresponding to the signals X1˜X4. The weight calculating unit 58 thenregards a sum of the multiplied signals X1˜X4 as an estimated signal ofa desired mobile station. The weight calculating unit 58 adjusts eachweight vector in such a way that minimizes an error between theestimated signal of the desired mobile station and the reference signaloutputted from the reference signal generating unit 55.

This is to say, the weight calculating unit 58 presents the receivedsignals X1˜X4 by using vector sequences “x₁(t)”, “x₂(t)”, “x₃(t)”, and“x₄(t)” which change over time, and presents weight vectorscorresponding to the signals X1˜X4 by using “w₁(t)”, “w₂(t)”, “w₃(t)” ,and “w₄(t)”. The weight calculating unit 58 then obtains the estimatedsignal “y(t)” by calculating Expression 3 below. Here, “t” shows a timerepresented in a unit of a time taken to receive one symbol within atime slot in the PHS standard.

Expression 3y(t)=w ₁(t−1)·x ₁(t)+w ₂(t−1)·x ₂(t)+w ₃ (t−1)·x ₃(t)+w ₄(t−1)·x ₄(t)

After obtaining the estimated signal “y(t)”, the weight calculating unit58 adjusts a value of “w(t−1)” within a predetermined range so as tominimize an error “e(t)” between the reference signal “d(t)” and theestimated signal “y(t)”. The adjusted weight vector is then regarded asa weight vector “w(t)” to be used in the next time unit. The error“e(t)” can be obtained by Expression 4 below.

Expression 4e(t)=d(t)−y(t)

Under the control of the control unit 80, the weight selecting unit 57sets a weight vector calculated by the weight calculating unit 58 duringthe signal reception from a mobile station as a weight vector thatmultiplies a quarter of a signal, which has been outputted from themodem unit 60 and corresponds to one mobile station.

Data Construction

The following describes the UW information stored in the UW storing unit90.

FIG. 4 shows a construction and example contents of the UW information.

As shown in the figure, the UW information associates each UW with adifferent assignment state of the UW. The UW information contains fourtypes of UWs, such as a 16-bit value of “0011110101001100” representedin binary notation. The assignment state is shown as a value whichspecifies a mobile station to which a UW is assigned, such as “USER 1”and “USER 2”, or as a value showing that a UW has not been assigned toany mobile stations.

Processing

The following describes the processing of the wireless base station 1000that has the above construction, focusing on the assignment of a UW to amobile station, which is a characteristic of the present invention.

FIG. 5 is a flowchart showing the processing of the wireless basestation 1000 when it receives a link channel assignment request from amobile station to have data transmission or phone conversation started.The processing shown in this flowchart is achieved under the control ofthe control unit 80.

When receiving, from a mobile station, a link channel assignment request(step S01) or a link channel reassignment request (step S02), thecontrol unit 80 searches for an available channel to be assigned to thismobile station (step S03). When finding no such channel (step S04), thecontrol unit 80 has an assignment reject notification sent to the mobilestation (step S08).

When finding a channel (step S04), the control unit 80 refers to the UWinformation in the UW storing unit 90 to specify one UW which has notbeen assigned to any mobile station, and updates the UW information byassociating the specified UW with the requesting mobile station (stepS05). The control unit 80 then has a channel assignment notificationsent to the mobile station (step S06). This channel assignmentnotification contains the associated UW and notifies that the linkchannel has been assigned to the mobile station. For instance, if thecontrol unit 80 receives a channel assignment request from a mobilestation during a phone conversation being performed by other two mobilestations with the UW storing unit 90 storing the UW information shown inFIG. 4, the control unit 80 updates the UW information by associating aUW “100111111100110” with a “USER 3” in step S05. After this in stepS06, the control unit 80 performs the control to transmit a channelassignment notification containing this UW “1000111111100110” andinformation which specifies the assigned channel, such as a time slotand a frequency.

After step S06, the control unit 80 sends the assigned UW to a referencesignal generating unit in a user processing unit, which is to performoperations for the mobile station to which the channel assignmentnotification has been sent (step S07). As a result, the reference signalgenerating unit 55 in the user processing unit 51 c, for instance,generates a reference signal, which contains this UW and is an idealsignal to be sent by the mobile station.

FIG. 6 shows the sequence of the link channel assignment in outlinebetween a mobile station and the wireless base station 1000.

As shown in the figure, when receiving the channel assignment requestfrom the mobile station (step S101), the wireless base station 1000performs the processing in FIG. 5, in which it sends a channelassignment notification containing the assigned UW to the mobile stationin step S06 (step S102).

Note that each mobile station has not only a construction conforming tothe conventional PHS standard but also a function to use, instead of aUW defined in the PHS standard, a UW contained in the received channelassignment notification so as to establish a physical slot and thentransfer communication data to/from a wireless base station using thephysical slot. The mobile station perform this function by having itsCPU execute a control program stored in memory to control other units ofthe mobile station.

In this way, the wireless base station 1000 sends a UW to a mobilestation with which communication is to be performed. This UW differsfrom UWs assigned to other mobile stations. The wireless base station1000 also uses this UW as a part of a reference signal used to separateand extract a signal sent from this mobile station.

Since each mobile station uses a UW sent from the wireless base station1000 as a UW conforming to the PHS standard to establish a physical slotand communicate via a T channel, the wireless base station 1000 cancommunicate with this mobile station while suppressing interference withother mobile stations and maintaining good communication quality usingthe SDM without needing to precisely stagger transmission times of thesemobile stations.

SECOND EMBODIMENT

The following describes a wireless base station of the secondembodiment.

The wireless base station of the second embodiment has basically thesame construction as the wireless base station 1000 of the firstembodiment (see FIG. 1), but differs from the first embodiment inoperation contents of a control unit 80 and in that UW information isnot generated and stored into a UW storing unit 90 until the wirelessbase station receives a UW from a mobile station.

Note that each mobile station of the present embodiment has not only aconstruction conforming to the conventional PHS standard but alsofunctions to determine an appropriate value to be used as a UW, send theUW to the wireless base station when requesting a channel assignment tothe base station, and use, instead of a UW defined in the PHS standard,the determined UW for establishing a physical slot and transferringcommunication data to/from the wireless base station. Each mobilestation achieves these functions by having its CPU execute a controlprogram stored in its memory to control other units contained in themobile station.

Processing

The following describes the processing of the wireless base station ofthe present embodiment. Here, the same reference numbers as in the firstembodiment are assigned to units common to the two embodiments.

FIG. 7 is a flowchart showing the processing of the wireless basestation when it receives a link channel assignment request from a mobilestation to start data transmission or telephone conversation with themobile station. The processing shown in this flowchart is performedunder the control of the control unit 80.

When receiving, from a mobile station, a link channel assignment request(step S11) or a link channel reassignment request (step S12), thecontrol unit 80 searches for a channel to be assigned to this mobilestation (step S13). Together with this request, the mobile station alsosends a UW to the wireless base station. When finding no such channel(step S14), the control unit 80 has an assignment reject notificationsent to the mobile station (step S18).

When finding an available channel (step S14), the control unit 80 has achannel assignment notification sent to the mobile station (step S15).This assignment notification contains information which specifies theassigned channel, such as a time slot and a frequency.

After sending the assignment notification, the control unit 80associates the UW, which has been sent from the mobile station togetherwith the channel assignment request, with this mobile station, andstores them into the UW storing unit 90 as UW information (step S16).The control unit 80 then has this UW outputted to a user processingunit, which is to perform operations for this mobile station (step S17).As a result, the reference signal generating unit 55 in the userprocessing unit 51 a, for instance, can generate a reference signal,which contains this UW and is an ideal signal estimated to have beensent from the mobile station.

FIG. 8 shows the sequence of the link channel assignment in outlinebetween a mobile station and the wireless base station.

As shown in the figure, when receiving the link channel assignmentrequest containing a UW from the mobile station (step S201), thewireless base station performs the processing shown in FIG. 7, in whichit sends a channel assignment notification to the mobile station in stepS15 (step S202).

In this way, the wireless base station receives, from a mobile stationwith which it is to start communication, a UW that is used to establisha physical slot defined in the PHS standard for communication via a Tchannel. The wireless base station then uses the received UW as a partof a reference signal to extract a signal sent from the mobile station.When each mobile station uses a different UW from other mobile stationswhose signals are SD-multiplexed, and sends this UW to the wireless basestation, the wireless base station can communicate with each mobilestation while suppressing interference with other mobile stations andmaintaining good communication quality.

Supplementary Explanation

The above embodiments have been used to describe the wireless basestation and the mobile station of the present invention although itshould be clear that the present invention is not limited to theseembodiments. Possible modifications are described below.

(1) The above embodiments describe the present invention, using awireless base station and a mobile station in the PHS system. Thepresent invention, however, may be applied to a communication system inwhich each mobile station sends/receives communication data containing aword for synchronization, which corresponds to a UW used to establish aphysical slot conforming to the PHS standard. The word forsynchronization should be a bit sequence used as an identifier.

(2) A UW is sent from the wireless base station 1000 to a mobile stationin the first embodiment while in the second embodiment a UW is sent froma mobile station to the wireless base station. Instead of such UWitself, identification information that specifies the UW, such asidentification numbers like “1”, “2”, “3”, and “4” may be used. In thiscase, it is necessary that both the wireless base station and a mobilestation are capable of obtaining the UW value based on theidentification information such as by performing a calculation. Forinstance, this identification information may be an unused bit sequencecontained in a channel assignment message defined in the PHS standard.

(3) The first embodiment states that the UW storing unit 90 stores UWinformation containing four fixed values as UWs in advance and that thecontrol unit 80 outputs a UW out of the four UWs to each referencesignal generating unit in the user processing units 51 a˜51 d. However,instead of having the UW storing unit 90 store fixed UW values, four UWvalues may be generated such as by having the control unit 80 generaterandom numbers and include them in the UW information.

(4) In the second embodiment, each mobile station determines a UW suchas by generating a random number, and then sends this UW to the wirelessbase station, which does not necessarily check the sent UW value.However, if the sent UW is the same as a UW used by another mobilestation whose signals are SD-multiplexed togther, the wireless basestation may send a channel assignment rejection notification whichnotifies the requesting mobile station that a UW other than the sent UWshould be used since the sent UW is the same as a UW of another mobilestation.

(5) On completing communication with a mobile station, the wireless basestation of the present invention may update the UW information to deletethe association of this mobile station with a stored UW although this isnot described in the above embodiments.

(6) The wireless base station determines a pattern of scrambling to beperformed for a security reason on body data (i.e., the content) ofcommunication with a mobile station although this is not described inthe above embodiments. Since a different scrambling pattern is used foreach mobile station, a signal determined by each scrambling pattern maybe included in a reference signal generated by a reference signalgenerating unit for each mobile station.

1. A wireless telephone, the wireless telephone being a communicationparty when communicating with a base station that extracts communicationdata relating to the communication party, the base station extractingthe communication data by: receiving a word for synchronization from thecommunication party and defining a reference signal containing the wordfor synchronization; obtaining a second signal estimated to be a signalrelating to the communication data by forming a directivity patternusing a plurality of first signals that are sequentially received via anantenna; sequentially calculating the directivity pattern based on thereference signal and the second signal; adjusting the second signal bysequentially adjusting the directivity pattern by reflecting a result ofthe calculation; and regarding the adjusted second signal ascommunication data sent from the communication party, the wirelesstelephone comprising: word-for-synchronization generating meansgenerating a word for synchronization that is used in communicationswith the wireless base station; link channel assignment requesting meanssending, to the wireless base station, a link channel assignment requesttogether with the word for synchronization generated by theword-for-synchronization generating means; link channel assignmentnotification reception means receiving a link channel assignmentnotification from the wireless base station in response to the linkchannel assignment request, the link channel assignment notificationcontaining information specifying an available channel; sending meansfor sending the word for synchronization generated by theword-for-synchronization generating means to the wireless base stationwhen performing communication with the wireless base station over thechannel specified by the link channel assignment notification, the wordfor synchronization being sent before main data that is a content of thecommunication.
 2. The wireless telephone as claimed in claim 1, whereinthe word-for-synchronization generating means generates the word forsynchronization by generating a random number.